Patent application title: MOLDING APPARATUS AND MOLDING METHOD

Abstract:

A molding apparatus for patterning a workpiece includes a first support
member for supporting the mold, a second support member arranged opposite
to the first support member, and a pressing mechanism for pressing the
mold and the work together using the support members to pattern the
workpiece. In this structure, either the surface of the first support
member for supporting the mold or the surface of the second support
member for supporting the workpiece is smaller in area than both surfaces
of the mold and the workpiece.

Claims:

1.-12. (canceled)

13. A molding method of patterning a workpiece using a mold, comprising
the steps of:attaching the mold to a first support member for supporting
the mold and attaching the workpiece to a second support member for
supporting the workpiece; andbringing the first and second support
members toward each other to press a patterned surface of the mold and a
work surface of the workpiece together so as to pattern the
workpiece,wherein the first support member has a first press surface with
outer edge, and the second support member has a second press surface with
outer edge, and the outer edges of at least one of the first press
surface or the second press surface are smaller in outer dimension than
the mold and the workpiece.

14. The molding method according to claim 13, wherein the first press
surface and the second press surface are arranged opposite to each other
along a press axis and have a plane symmetry.

15. The molding method according to claim 13, wherein the outer edges of
both the first press surface and the second press surface are smaller in
outer dimension than the mold and the workpiece.

16. The molding method according to claim 13, wherein the first or second
support member is provided with a holding member at its periphery.

17. The molding method according to claim 16, wherein the holding member
is a material with a Young's modulus low enough to reduce a pressing
force.

18. A molding method of patterning a workpiece using a mold, comprising
the steps of:attaching the mold to a first support member for supporting
the mold and attaching the workpiece to a second support member for
supporting the workpiece; andbringing the first and second support
members toward each other to press a patterned surface of the mold and a
work surface of the workpiece together so as to pattern the
workpiece,wherein a press surface of the first support member on a mold
side has a first press surface with an outer edge smaller in outer
dimension than the mold and the workpiece, andthe press surface of the
first support member and a press surface of the second support member are
substantially symmetrical to each other.

Description:

BACKGROUND OF THE INVENTION

[0001]1. Field of the Invention

[0002]The present invention relates to a press molding apparatus and a
press molding method, for transferring the features of a mold to a
workpiece under the application of pressure.

[0003]2. Description of the Related Art

[0004]In recent years, micro-fabrication technology for press transferring
fine structures on a mold to a workpiece, such as resin or metal, have
been developed and become a focus of attention. This technology, called
nano-imprint or nano-embossing, has a resolution on the order of several
nanometers. In addition, it can mold 3D structures on a wafer by one
operation. For these reasons, this technology is expected to be
applicable to a wide variety of fields, such as the next-generation
semiconductor fabrication, the fabrication of optical elements like
photonic crystals, and the fabrication of biochips such as μ-TAS
chips.

[0005]Japanese patent laid-open application No. Hei 11 (1999)-033800
proposes a method of pressing a mold into a resist on a semiconductor
wafer to create an imprint pattern so as to produce a pattern on the
semiconductor wafer through the process of ion milling.

[0006]An article, "Uniformity in Patterns Imprinted Using Photo-Curable
Liquid Polymer" by Hiroshi Hiroshima, et al, Jpn. J. Appl. Phys. Vol. 41
(2002) 4173-4177, also proposes a method in which a sapphire block is
used to press a mold smaller in area than the block, and expose it to UV
rays to cure UV curing resin so as to produce a pattern.

[0007]The following describes problems in the above-mentioned molding
technology with reference to FIG. 5.

[0008]FIG. 5 shows a typical example of the structure of the prior art
technology. A mold 106 is typically micro-fabricated on a wafer of Si or
SiO2 by EB lithography, FIB, X-ray lithography, etc, or replicated
by Ni electroforming. A workpiece, or work, 107 is typically an Si
semiconductor wafer coated with resin, or a resin plate. The mold 106 and
the work 107 are sandwiched between a mold pressing member 104 and a work
pressing member 109, and pressed together by means of a press mechanism
(not shown). The mold 106 and the work 107 are held typically by
evacuating air (110) from grooves or holes provided in each pressing
member.

[0009]In this structure, since the mold 106 is smaller in area than the
mold pressing member 104, the work 107, and the work pressing member 109,
the molding force is concentrated around the periphery of the mold 106
and gradually reduced to the center portion. The above-mentioned wafer is
thin, with a thickness of 1 mm or less. Therefore, the uneven
distribution of molding force almost directly affects the contact surface
of the mold 106 and the work 107, causing an unevenness of processed
depths. Further, the mold force is also reduced around the grooves or
holes provided for evacuating air 110 for the same reason.

[0010]Such a structure is likely to cause stress concentration at the
edges of the mold 106. The above-mentioned wafer material such as Si or
SiO2 is fragile or brittle, and in many cases, a brittle fracture
starts from a point of the wafer material. Further, the point at which
the brittle fracture started also hastens the damage to the pressing
part, increasing maintenance costs.

SUMMARY OF THE INVENTION

[0011]In order to solve the above-mentioned problems, the present
invention uses the following means.

[0012]That is, according to the present invention, there is provided a
molding apparatus for patterning a workpiece using a mold. The apparatus
includes a first support member for supporting the mold, a second support
member, arranged opposite to the first support member, for supporting the
workpiece between the first support member and the second support member
itself, and a pressing mechanism for pressing the mold and the workpiece
together to bring the mold and the workpiece in contact with each other
so as to pattern the workpiece.

[0013]In this structure, at least either the surface of the first support
member for supporting the mold or the surface of the second support
member for supporting the workpiece is smaller in area than both of the
mold and the workpiece.

[0014]In another aspect of the present invention, there is provided a
molding apparatus for transferring the recessed and raised features of a
mold to a workpiece. The apparatus includes a first support member for
supporting the mold, and a second support member, arranged opposite to
the first support member, for supporting the workpiece.

[0015]In this structure, the surface of the first support member on the
mold side is smaller in area than the surfaces of the mold and the
workpiece, and the surface of the second support member on the workpiece
side is smaller in area than the surfaces of the mold and the workpiece.

[0016]In yet another aspect of the present invention, there is provided a
molding apparatus for transferring the recessed and raised features of a
mold to a workpiece. The apparatus includes a first support member for
supporting the mold, and a second support member, arranged opposite to
the first support member, for supporting the workpiece.

[0017]In this structure, the surface of the first support member on the
mold side is smaller in area than the surface of the mold on the first
support member side, and the surface of the first support member on the
mold side and the surface of the second support member on the workpiece
side are substantially the same as each other.

[0018]The "substantially the same" means not only the same shape, but also
similar shapes between which there is a difference within 10 percent,
preferably 5 percent, and further preferably within 2 percent. Even when
the first and second support members have the same shape (same area), it
is preferable that the area be smaller than that of the mold.

[0019]Further features and advantages of the present invention will become
apparent from the following description of exemplary embodiments (with
reference to the attached drawings).

BRIEF DESCRIPTION OF THE DRAWINGS

[0020]FIG. 1 is a cross sectional view for explaining the structure of an
apparatus according to a first embodiment of the present invention.

[0021]FIG. 2 is a cross sectional view for explaining a pressed state in
the structure according to the first embodiment of the present invention.

[0022]FIG. 3 is a cross sectional view for explaining the structure of an
apparatus according to a second embodiment of the present invention.

[0023]FIG. 4 is a cross sectional view for explaining a pressed state in
the structure according to the second embodiment of the present
invention.

[0024]FIG. 5 is a cross sectional view for explaining the problems of the
prior art technology.

DESCRIPTION OF THE EMBODIMENTS

[0025]In preferred embodiments of the present invention, any of the
above-mentioned structures is applied in such a manner that at least
either of the press surface of the first support member and the press
surface of the second support member is made smaller in area than both of
a mold and a work. Therefore, since pressure is applied to an inner area
smaller in area than the outside circumference of each of the mold and
the work, stress concentration around the outside circumference of the
mold or the work can be prevented or at least reduced, reducing the
possibility of damage not only to the mold and the work but to the press
members.

[0026]Further, if both of the press surfaces are made equal in outer
dimensions to each other and placed axially so that the press surfaces
will be symmetric to the contact surface of the mold and the work, the
deformation of the mold and the work can be prevented, thereby further
preventing the damage to the mold and the work. In addition, if the press
members are made in the form of columns, the uniformity of molding force
can be improved, enabling the patterning of the work with an even depth.

[0027]Furthermore, if a holding member with a low Young's modulus is
provided on the outside of work surface so that the work will be held by
reducing pressure between the press member and the hold member, the mold
and the work can be held without hardly affecting the distribution of
molding force. This improves the evenness of the molding force, enabling
the patterning of the work with an even depth. Since the holding member
with a low Young's modulus is provided so that the work will be held by
reducing pressure between the press member and the hold member, the mold
and the work can be held while maintaining the evenness of the molding
force.

First Embodiment

[0028]The first embodiment of the present invention will now be described
with reference to FIGS. 1 and 2.

[0029]As shown in FIG. 1, the mold 106 is arranged opposed (or opposite)
to a work (workpiece) 107 made by coating resin on an Si wafer. The mold
pressing member (first support member) 104 and the work pressing member
(second support member) 109 are surrounded with a space by a mold holding
member 105 and a work holding member 108, respectively. Air is evacuated
(110) from the space to hold the mold 106 and the work 107. Both of the
pressing members are connected to each other through press part support
members 103, a press mechanism 102, and an apparatus frame or casing 101
that receives a reactive force from the press mechanism 102. The press
mechanism 102 applies pressure between the mold 106 and the work 107
using a pneumatic cylinder to transfer the surface features of the mold
106 into the resin on the work 107. The material of each member is steel
or stainless steel unless otherwise noted. In FIG. 1, the press mechanism
102 moves the mold, but it may move the work, or both.

[0030]In the embodiment, since the mold 106 has a circular surface smaller
in area than that of the work 107, the mold pressing member 104 is also
made in the form of a cylinder smaller in diameter than the mold 106. The
work pressing member 109 is made in the form of a cylinder, the diameter
of which is smaller than that of the work 107 but larger than that of the
mold pressing member 104. When both pressing members are arranged to
opposed each other with respect to the pressing axis, it is particularly
preferable that press surfaces of both pressing members or
cross-sectional planes nominal to the pressing axis have a plane
symmetry. FIG. 2 shows a state in which press molding is carried out
using the above-mentioned structure. In this case, stress concentration
at the edges of the mold 106 and the work 107 can be avoided, preventing
brittle fracture starting from these edges. This structure can also
reduce the unevenness of molding force caused by providing holes or
grooves for evacuating air 110. Further, the material of the mold holding
member 105 and the work holding member 108 has a Young's modulus low
enough to have little effect on the distribution of the molding force.

[0031]In the disclosed embodiment, cylinder-shaped pressing members are
used, but any other shape is selectable as appropriate, such as the shape
of a quadratic prism or a circular pipe, depending on the shape of the
mold 106 or the work 107, or the shape of a molded area. Further, the
mold holding member 105 and the work holding member 108 are made of
resin, but any other structure can be adopted as long as it has little
effect on the distribution of molding force, such as a metal ring pressed
by a spring.

Second Embodiment

[0032]The second embodiment of the present invention will now be described
with reference to FIGS. 3 and 4.

[0033]As shown in FIG. 3, the mold 106 is arranged to opposed the work
107, which is made by coating resin on an Si wafer. The mold pressing
member 104 and the work pressing member 109 are surrounded with a space
by the mold holding member 105 and the work holding member 108,
respectively, made of fluorocarbon resin. Air is evacuated (110) from the
space to hold the mold 106 and the work 107. Both of the pressing members
are connected to each other through the press part support members 103,
the press mechanism 102, and the casing 101 that receives a reactive
force from the press mechanism 102. The press mechanism 102 applies
pressure between the mold 106 and the work 107 using a pneumatic cylinder
to transfer the surface features of the mold 106 into the resin on the
work 107. The material of each member is steel or stainless steel unless
otherwise noted.

[0034]In the embodiment, since the mold 106 has a smaller circular area
than the work 107, the mold pressing member 104 and the work pressing
member 109 are also made in the form of cylinders smaller in diameter
than the mold 106, and axially arranged. To be more specific, both of the
pressing members are in the form of cylinders of 20 mm in diameter and 30
mm in height with respect to the mold of 25 mm in diameter, respectively.
FIG. 4 shows a state in which press molding is carried out using the
above-mentioned structure. In this case, stress concentration at the
edges of the mold 106 and the work 107 can be reduced or even avoided,
preventing brittle fracture starting from these edges. This structure can
also reduce the unevenness of molding force caused by providing holes or
grooves for evacuating air 110. Further, the material of the mold holding
member 105 and the work holding member 108 has a Young's modulus low
enough to have little or no effect on the distribution of the molding
force.

[0035]Furthermore, since the distribution of the molding force in this
structure comes very close to the axial stress distribution on the
cross-sectional planes nominal to the pressing axis when the cylinders
are pressed together in the axial direction, a very even stress
distribution can be obtained even when the pressing members have a high
Young's modulus. For example, if the mold and the work are an Si wafer of
1 mm thick, respectively, and are pressed by the pressing members made of
steel, the distribution of the molding force can be reduced to about 5
percent. This structure is particularly suitable for high-precision
fabrication.

[0036]Although in the disclosed embodiment cylinder-shaped press members
are used, but any other shape is selectable depending on the shape of the
mold 106 or the work 107, or the shape of a molded area. For example, a
quadratic prism or cylinder for patterning a recording medium, or a
cylinder having a hole in the center for patterning a recording medium
may be selected. Further, although in the embodiment the mold holding
member 105 and the work holding member 108 are made of resin, any other
structure can be adopted as long as it has little effect on the
distribution of molding force, such as, for example, a metal ring pressed
by a spring.

[0037]While the present invention has been described with reference to
exemplary embodiments, it is to be understood that the invention is not
limited to the disclosed embodiments. On the contrary, the invention is
intended to cover various modifications and equivalent arrangements
included within the spirit and scope of the appended claims. The scope of
the following claims is to be accorded the broadest interpretation so as
to encompass all such modifications and equivalent structures and
functions.